Camera lens systems

ABSTRACT

In an image forming optical lens system comprising in order from the object end a first lens group of at least two components, a second lens group which has a positive focal length and comprises in order from the object end a first component of positive power, a second component of negative power and a third component of positive power, and a third lens group of at least one component, the components of the lens system are made of at least two different kinds of materials having differences in dispersion of 0.0055 at the greatest from one another and the first to third components of the second lens group are made of materials different in dispersion from one another.

This application is a continuation of application Ser. No. 08/426,135, filed Apr. 21, 1995, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a lens system for use with a camera such as utilizes a charge coupled device (CCD), an image pick-up and a film as a recording medium of optical images.

2. Description of Related Art

In most cases of designing lens systems used suitably for ultraviolet rays in consideration of transmittance, materials of lens components are limited to crystals such as fluorite and silicate glass. If the lens system is comprised of lens components made of such crystals, not only, because of small differences in dispersion among the lens components, it is difficult to reduce color aberrations of the lens system but, because of low refracting indices of the lens components, the lens system tends to have a large Petzval sum. Consequently, the lens system has been often used as an object lens for, for instance, a microscope which ordinarily needs a narrow angle of view. In addition, some kinds of crystals render surfaces of lens components with small radii difficult to be precisely formed due to their structure or impossible to be made concave. These restraints imposed on shapes of lens components enhance aggravation of aberrations.

One of various efforts having been made to eliminate such problems is that described in Japanese Laid-Open Patent No. 48-34531. However, the lens system as described in Japanese Laid-Open Patent No. 48-34531 still has disadvantages such as a narrow angle of view of, for instance, approximately 29 degrees, an insufficiently corrected Petzval sum and an insufficient correction of color aberrations across, in particular, the intended wavelength range of ultraviolet rays.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved wide angle lens system which is sufficiently corrected in color aberrations and has a sufficiently suppressed Petzval sum even if the lens system is comprised of lens components made of materials having low dispersion.

Briefly stated, the invention in one form thereof consists of a wide angle lens system which comprises in order from the object end a first lens group of at least two components, a second lens group which has a positive focal length and comprises in order from the object end a first component of positive power, a second component of negative power and a third component of positive power, and a third lens group of at least one component. The second lens group may comprise three singlets, or otherwise include a doublet or a triplet. The components of the lens system are made of at least two different kinds of materials having differences in dispersion of 0.0055 at the greatest from one another. Together, the first to third components of the second lens group are made of materials different in dispersion from one another.

A wide angle lens system embodying the present invention may be designed for a wide range of angles of view by satisfying the following conditions:

    -0.75<F/F1<0.75                                            (I)

    0.3<F/F2<1.55                                              (II)

    -1.50<F/F3<0.15                                            (III)

    0.9<F2/f1<5.0                                              (IV)

    1.2<|F2/f2|<7                            (V)

    0.9<F2/f3<2.4                                              (VI)

where F is the overall focal length of the lens system, F1, F2 and F3 are the focal length of the first, second and third lens groups, respectively, and f1, f2 and f3 are the focal length v of the--the first, second and third components of the second lens group, respectively.

The dispersion v of the lens material N is expressed as follows:

    v=N.sub.F -N.sub.C

where N_(F) and N_(C) are the refractive indices of lens materials for an F-spectrum of wavelength of 486.13 nm and a C-spectrum of wavelength of 656.27 nm, respectively.

The transmittance of each lens material of a thickness of 10 mm is preferred to be at least 50% for light rays of wavelength from 300 to 800 nm. fluorite glass and silicate glass for these components are preferred. Specifically, the third lens group is preferred to comprise first and third components made of fluorite glass and a second component made of silicate glass.

The parameters set forth are necessary for suitably balancing the aberrations of the lens system. Together, the conditions prevent or significantly reduce aggravation of spherical aberration, coma, distortion and color aberrations.

The first conditions (I)-(III) are necessary for suitable distribution of power for suitably balancing the aberrations of the optical system. If the lower limit of the first condition (I) is exceeded, the first lens group has a too strong negative power, so that distances of paraxial rays from the optical axis incident upon the second lens group are too large. This leads to aggravation of spherical aberration. On the other hand, if the upper limit of the first condition (I) is exceeded, the first lens group has a too strong positive power, so that distances of paraxial rays from the optical axis incident upon the second lens group are too small. This leads to aggravation of color aberrations of the second lens group. Further, that makes the back focal length of the optical system short which is not always desirable.

The second condition (II) defines the power of the second lens group. If the lower limit of the second condition (II) is exceeded, the second lens group has a too weak positive power, so that the second lens group suffers aggravation of color aberrations. If the upper limit of the second condition (II) is exceeded, the second lens group has a strong positive power and a too small radius, being rendered difficult to be corrected in color aberrations. Further, if lens components are made of fluorite glass, it is difficult to finish the surfaces of the lens components with a high precision.

Because, in the optical system, the Petzval sum is corrected by the third lens group which allows high paraxial rays to enter, if the lower limit of the third condition (III) is exceeded, the third lens group has a too strong negative power, not only making the back focal length of the optical system short which is not always desirable but also being rendered difficult to be corrected in coma and distortion. On the other hand, if the upper limit of the third condition (III) is exceeded, the third lens group has a too strong positive power, making the Petzval sum too large. This increases aggravation of field curvature of the system.

Together, if the lower limits of the fourth to sixth conditions (IV)-(VI) are exceeded all together, the second lens group has a too weak power, increasing aggravation of color aberrations. On the other hand, if the upper limits of the fourth to sixth conditions (IV)-(VI) are exceeded all together, the second lens group has a too strong power and a too small radius, rendering the optical system difficult to be corrected in spherical aberration. In addition, if lens components are made of fluorite glass, it is difficult to finish the surfaces of the lens components with a high precision.

The optical system of the present invention may comprises lens components made of silica glass and/or fluorite glass which have high transmittance in a range of wavelength of ultraviolet light and a small difference in dispersion, preventing or significantly reducing of various aberrations. The utilization of materials which have transmittance higher than approximately 50% for light of wavelength between 300 and 800 nm enables the optical system to be used over a range from ultraviolet light to visible light.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will be clearly understood from the following description with respect to a preferred embodiment thereof when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic side view of a lens system embodying the present invention;

FIG. 2 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 1;

FIG. 3 is a diagrammatic side view of a lens system of a second embodiment of the present invention;

FIG. 4 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 3;

FIG. 5 is a diagrammatic side view of a lens system of a third embodiment of the present invention;

FIG. 6 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 5;

FIG. 7 is a diagrammatic side view of a lens system of a fourth embodiment of the present invention;

FIG. 8 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 7;

FIG. 9 is a diagrammatic side view of a lens system of a fifth embodiment of the present invention;

FIG. 10 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 9;

FIG. 11 is a diagrammatic side view of a lens system of a sixth embodiment of the present invention;

FIG. 12 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 11;

FIG. 13 is a diagrammatic side view of a lens system of a seventh embodiment of the present invention;

FIG. 14 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 13;

FIG. 15 is a diagrammatic side view of a lens system of a eighth embodiment of the present invention;

FIG. 16 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 15;

FIG. 17 is a diagrammatic side view of a lens system of a ninth embodiment of the present invention;

FIG. 18 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 17;

FIG. 19 is a diagrammatic side view of a lens system of a tenth embodiment of the present invention;

FIG. 20 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 19;

FIG. 21 is a diagrammatic side view of a lens system of an eleventh embodiment of the present invention;

FIG. 22 shows diagrams of spherical aberration, astigmatism, distortion and magnification color aberration of the lens system of FIG. 21; and

FIG. 23 shows a diagram of transmittance of various glass.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following prescription tables where various versions of the invention are set forth, the reference L followed by an arabic numeral indicates the lens component progressively from the object end to the image end of the photographic lens system. The reference S followed by an arabic numeral indicates the lens surface progressively from the object end to the image end of the zoom lens system. The reference radius numbers r are the progressive lens surface radii. The reference N and d are the index of refraction of the lens component for i-spectrum and the progressive axial distance between adjacent surfaces, respectively.

FIGS. 1-8 show various versions of a first embodiment of the present invention. The lens systems are composed of three lens groups, namely first and second and third lens groups G1, G2 and G3 arranged along the optical axis X in order from the object end to the image end. The first lens group G1 comprises in order from the object end two, namely first and second, lens components L1 and L2 between which a lens stop D is stationarily disposed. The second lens group G2 comprises in order from the object end a third bi-convex lens component L3, a fourth bi-concave lens component L4 and a fifth bi-convex lens component L5. The third lens group G3 comprises two, namely sixth and seventh, lens components L6 and L7. A parallel flat cover plate G4 is disposed at a certain distance behind the image end surface of the seventh lens component L7. These optical components including the lens components L1-L7 and the parallel flat cover plate G4 are in fixed relation.

In the lens system shown in FIG. 1, the lens stop D is stationarily disposed at a distance of 0.9857 mm in front of the object end surface of the second lens component L2.

The lens system as shown in FIG. 1 is substantially described in Table I.

                  TABLE I     ______________________________________     F No. = 2.5 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 23.9660     L.sub.1                    d.sub.1  = 9.9262                                              1.47454              S2     r.sub.2  = 11.2800                                d.sub.2  = 25.9857              S3     r.sub.3  = 52.4481     L.sub.2                    d.sub.3  = 3.7473                                              1.44491              S4     r.sub.4  = -22.0621                                d.sub.4  = 0.1              S5     r.sub.5  = 15.9527     L.sub.3                    d.sub.5  = 5.4006                                              1.44491              S6     r.sub.6  = -16.6354                                d.sub.6  = 0.7501              S7     r.sub.7  = -13.0937     L.sub.4                    d.sub.7  = 1.0                                              1.47454              S8     r.sub.8  = 9.5032                                d.sub.8  = 1.0001              S9     r.sub.9  = 11.3864     L5                         d.sub.9  = 6.7394                                              1.44491              S10    r.sub.10  = -11.1132                                d.sub.10  = 0.9999              S11    r.sub.11  = -13.9526     L.sub.6                    d.sub.11  = 1.0                                              1.47454              S12    r.sub.12  = 9.6928                                d.sub.12  = 1.0              S13    r.sub.13  = 11.2385     L.sub.7                    d.sub.13  = 4.8019                                              1.44491              S14    r.sub.14  = ∞                                d.sub.14  = 2.0              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.55                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.76 57.244   22.4    -24.769                                   19.31 -11.429                                                13.913     ______________________________________

The lens system depicted in FIG. 1 and described in Table I has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.54   1.15      -1.04  1.16     1.96  1.61     ______________________________________

As apparent from the above, the lens system shown in FIG. 1 satisfies the conditions (I)-(VI). Together, the lens components L2, L3, L5 and L7 are made of fluorite glass and the lens components L1, L4 and L6 and the cover glass G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 2 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 1. As apparent in FIG. 2, the lens system has superior correction for these aberrations.

FIG. 3 shows a second version of the first embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 1.3689 mm in front of the object end surface of the second lens component L2. The second lens group G2 includes a doublet comprising the fourth and fifth lens components L4 and L5 cemented together.

The lens system as shown in FIG. 3 is substantially described in Table II.

                  TABLE II     ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 22.6687     L.sub.1                    d.sub.1  = 10.000                                              1.47454              S2     r.sub.2  = 10.5512                                d.sub.2  = 26.3689              S3     r.sub.3  = 212.6157     L.sub.2                    d.sub.3  = 3.7200                                              1.44491              S4     r.sub.4  = -17.9567                                d.sub.4  = 0.100              S5     r.sub.5  = 17.2749     L.sub.3                    d.sub.5  = 5.0841                                              1.44491              S6     r.sub.6  = -17.7102                                d.sub.6  = 0.7500              S7     r.sub.7  = -14.0756     L.sub.4                    d.sub.7  = 1.0000                                              1.47454              S8     r.sub.8  = 8.164                                d.sub.8  = 0              S9     r.sub.9  = 8.164     L5                         d.sub.9  = 8.3860                                              1.44491              S10    r.sub.10  = -11.8778                                d.sub.10  = 0.9999              S11    r.sub.11  = -12.4212     L.sub.6                    d.sub.11  = 1.0000                                              1.47454              S12    r.sub.12  = 10.6415                                d.sub.12  = 1.0000              S13    r.sub.13  = 11.8335     L.sub.7                    d.sub.13  = 4.0417                                              1.44491              S14    r.sub.14  = -1764.3175                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.75 52.551   22.391  -23.624                                   20.542                                         -10.765                                                12.509     ______________________________________

The lens system depicted in FIG. 3 and described in Table II has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.49   1.15      -1.09  1.09     2.08  1.79     ______________________________________

As apparent from the above, the lens system shown in FIG. 3 satisfies the conditions (I)-(VI). Together, the lens components L2, L3, L5 and L7 are made of fluorite glass and the lens components L1, L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 4 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 3. As apparent in FIG. 4, the lens system has superior correction for these aberrations.

FIG. 5 shows a third version of the first embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 1.4018 mm in front of the object end surface of the second lens component L2. The second lens group G2 includes a doublet comprising the third and fourth lens components L3 and L4 cemented together.

The lens system as shown in FIG. 5 is substantially described in Table III.

                  TABLE III     ______________________________________     F No. = 2.5 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 24.9171     L.sub.1                    d.sub.1  = 9.9358                                              1.47454              S2     r.sub.2  = 11.4855                                d.sub.2  = 26.4008              S3     r.sub.3  = 320.9305     L.sub.2                    d.sub.3  = 3.567                                              1.44491              S4     r.sub.4  = -19.9207                                d.sub.4  = 0.1001              S5     r.sub.5  = 13.9293     L.sub.3                    d.sub.5  = 6.6087                                              1.44491              S6     r.sub.6  = -13.2100                                d.sub.6  = 0              S7     r.sub.7  = -13.2100     L.sub.4                    d.sub.7  = 1.0131                                              1.47454              S8     r.sub.8  = 9.6419                                d.sub.8  = 1.0061              S9     r.sub.9  = 9.8346     L5                         d.sub.9  = 6.3403                                              1.44491              S10    r.sub.10  = -14.4150                                d.sub.10  = 1.0033              S11    r.sub.11  = -11.8551     L.sub.6                    d.sub.11  = 1.0006                                              1.47454              S12    r.sub.12  = 9.5828                                d.sub.12  = 1.0031              S13    r.sub.13  = 11.6447     L.sub.7                    d.sub.13  = 3.8428                                              1.44491              S14    r.sub.14  = -7240.6751                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.76 66.051   20.125  -20.608                                   16.496                                         -11.5  14.273     ______________________________________

The lens system depicted in FIG. 5 and described in Table III has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.39   1.28      -1.25  1.22     1.75  1.41     ______________________________________

As apparent from the above, the lens system shown in FIG. 5 satisfies the conditions (I)-(VI). Together, the lens components L2, L3, L5 and L7 are made of fluorite glass and the lens components L1, L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 6 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 5. As apparent in FIG. 6, the lens system has superior correction for these aberrations.

FIG. 7 shows a fourth version of the first embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 1.3206 mm in front of the object end surface of the second lens component L2. The second lens group G2 includes a triplet comprising the third, fourth and fifth lens components L3, L4 and L5 cemented together.

The lens system as shown in FIG. 7 is substantially described in Table IV.

                  TABLE IV     ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 22.4734     L.sub.1                    d.sub.1 = 10.0088                                              1.47454              S2     r.sub.2  = 11.0857                                d.sub.2  = 23.4071              S3     r.sub.3  = 132.1196     L.sub.2                    d.sub.3  = 3.4406                                              1.44491              S4     r.sub.4  = -20.0776                                d.sub.4  = 0.1000              S5     r.sub.5  = 14.6176     L.sub.3                    d.sub.5  = 6.1359                                              1.44491              S6     r.sub.6  = -11.7794                                d.sub.6  = 0              S7     r.sub.7  = -11.7794     L.sub.4                    d.sub.7  = 0.9498                                              1.47454              S8     r.sub.8  = 8.4994                                d.sub.8  = 0              S9     r.sub.9  = 8.4994     L.sub.5                    d.sub.9  = 6.9201                                              1.44491              S10    r.sub.10  = -14.7415                                d.sub.10  = 1.3550              S11    r.sub.11  = -12.2623     L.sub.6                    d.sub.11  = 4.8411                                              1.47454              S12    r.sub.12  = 9.4213                                d.sub.12  = 1.2466              S13    r.sub.13  = 11.3787     L.sub.7                    d.sub.13  = 4.2154                                              1.44491              S14    r.sub.14  = 15532.5120                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.75 61.310   21.107  -21.458                                   15.917                                         -10.148                                                13.275     ______________________________________

The lens system depicted in FIG. 7 and described in Table III has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.42   1.22      -1.20  1.33     2.08  1.59     ______________________________________

As apparent from the above, the lens system shown in FIG. 7 satisfies the conditions (I)-(VI). Together, the lens components L2, L3, L5 and L7 are made of fluorite glass and the lens components L1, L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 8 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 7. As apparent in FIG. 8, the lens system has superior correction for these aberrations.

FIGS. 9-18 show various versions of a second embodiment of the present invention. The lens systems are composed of three lens groups, namely first and second and third lens groups G1, G2 and G3 arranged along the optical axis X in order from the object end to the image end. The first lens group G1 comprises in order from the object end two, namely first and second, lens components L1 and L2 The second lens group G2 comprises in order from the object end a third bi-convex lens component L3, a fourth bi-concave lens component L4 and a fifth bi-convex lens component L5. The third lens group G3 comprises one or two, namely sixth and seventh, lens components L6 and L7. A lens stop D is stationarily disposed between the first and second lens groups G1 and G2. A parallel flat cover plate G4 is disposed at a certain distance behind the image end surface of the sixth or seventh lens component L6 or L7. These optical components including the lens components L1-L7 and the parallel flat cover plate G4 are in fixed relation.

FIG. 9 shows a first version of the second embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.5004 mm in front of the object end surface of the third lens component L3. The third lens group G3 comprises two, namely sixth and seventh, lens components L6 and L7.

The lens system as shown in FIG. 9 is substantially described in Table V.

                  TABLE V     ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 23.8147     L.sub.1                    d.sub.1 = 1.0026                                              1.47454              S2     r.sub.2  = 10.0929                                d.sub.2 =  1.2583              S3     r.sub.3  = 12.4516     L.sub.2                    d.sub.3  = 4.2303                                              1.44491              S4     r.sub.4  = 142.6490                                d.sub.4  = 9.3229              S5     r.sub.5  = 17.2963     L.sub.3                    d.sub.5  = 3.6873                                              1.44491              S6     r.sub.6  = -12.1061                                d.sub.6  = 1.2596              S7     r.sub.7  = -9.8721     L.sub.4                    d.sub.7  = 1.1823                                              1.47454              S8     r.sub.8  = 9.6330                                d.sub.8  = 1.2458              S9     r.sub.9  = 19.9700     L.sub.5                    d.sub.9  = 4.2708                                              1.44491              S10    r.sub.10  = -11.6384                                d.sub.10  = 0.1003              S11    r.sub.11  = 18.4670     L.sub.6                    d.sub.11  = 5.0541                                              1.47454              S12    r.sub.12  = -10.3953                                d.sub.12  = 0.7458              S13    r.sub.13  = -11.0881     L.sub.7                    d.sub.13  = 5.3058                                              1.44491              S14    r.sub.14  = 9.8022                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.75 143.056  33.013  -99.038                                   16.507                                         -9.914 17.194     ______________________________________

The lens system depicted in FIG. 9 and described in Table V has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.18   0.78      -0.26  2.00     3.33  1.92     ______________________________________

As apparent from the above, the lens system shown in FIG. 9 satisfies the conditions (I)-(VI). Together, the lens components L2, L3 and L5 are made of fluorite glass and the lens components L1, L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 10 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 9. As apparent in FIG. 10, the lens system has superior correction for these aberrations.

FIG. 11 shows a fifth version of the embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.3 mm in front of the object end surface of the third lens component L3. The third lens group G3 comprises a single lens component L6.

The lens system as shown in FIG. 11 is substantially described in Table VI.

                  TABLE VI     ______________________________________     F No. = 2.504 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 14.2465     L.sub.1                    d.sub.1 = 4.0484                                              1.47454              S2     r.sub.2  = -19.6229                                d.sub.2 =   0.5644              S3     r.sub.3  = -15.6487     L.sub.2                    d.sub.3  = 1.0000                                              1.44491              S4     r.sub.4  = 24.5485                                d.sub.4  = 1.7371              S5     r.sub.5  = 9.8040     L.sub.3                    d.sub.5  = 4.1775                                              1.44491              S6     r.sub.6  = -11.6842                                d.sub.6  = 0.5320              S7     r.sub.7  = -10.2333     L.sub.4                    d.sub.7  = 3.2945                                              1.47454              S8     r.sub.8  = 7.8683                                d.sub.8  = 1.3165              S9     r.sub.9  = 23.6511     L.sub.5                    d.sub.9  = 3.1266                                              1.44491              S10    r.sub.10  = -17.6213                                d.sub.10  = 1.0506              S11    r.sub.11  = 8.8540     L.sub.6                    d.sub.11  = 4.5398                                              1.47454              S12    r.sub.12  = 7.5565                                d.sub.12  = 2.0000              S13    r.sub.13  = ∞     G4                         d.sub.13  = 2.5500                                              1.47454              S14    r.sub.14  = ∞     F     F1       F2      F3     f1    f2     f3     ______________________________________     25.75 117.045  35.764  858.333                                   12.505                                         -8.941 23.223     ______________________________________

The lens system depicted in FIG. 11 and described in Table VI has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.22   0.72      0.03   2.86     4.00  1.54     ______________________________________

As apparent from the above, the lens system shown in FIG. 11 satisfies the conditions (I)-(VI). Together, the lens components L2, L3 and L5 are made of fluorite glass and the lens components L1 L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 12 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 11. As apparent in FIG. 12, the lens system has superior correction for these aberrations.

FIG. 13 shows a third version of the second embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.3 mm in front of the object end surface of the third lens component L3. The third lens group G3 comprises a single lens component L6.

The lens system as shown in FIG. 13 is substantially described in Table VII.

                  TABLE VII     ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 14.7844     L1                         d.sub.1  = 4.0110                                              1.47454              S2     r.sub.2  = -20.4636                                d.sub.2  = 0.4906              S3     r.sub.3  = -18.2579     L2                         d.sub.3  = 1.0000                                              1.44491              S4     r.sub.4  = 32.3312                                d.sub.4  2.0142              S5     r.sub.5  = 10.4750     L3                         d.sub.5  = 4.6115                                              1.44491              S6     r.sub.6  = -7.5771                                d.sub.6  = 0              S7     r.sub.7  = -7.5771     L4                         d.sub.7  = 3.5961                                              1.47454              S8     r.sub.8  = 7.6524                                d.sub.8  = 1.5227              S9     r.sub.9  = 43.7342     L5                         d.sub.9  = 2.9291                                              1.44491              S10    r.sub.10  = -17.1000                                d.sub.10  = 0.1000              S11    r.sub.11  = 8.7618     L6                         d.sub.11  = 5.0002                                              1.47454              S12    r.sub.12  = 7.4823                                d.sub.12  = 2.0000              S13    r.sub.13  = ∞     G4                         d.sub.13  = 2.5500                                              1.47454              S14    r.sub.14  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 71.528   50.490  429.167                                   10.607                                         -7.570 27.742     ______________________________________

The lens system depicted in FIG. 13 and described in Table VII has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.36   0.51      0.06   4.76     6.67  1.82     ______________________________________

As apparent from the above, the lens system shown in FIG. 13 satisfies the conditions (I)-(VI). Together, the lens components L2, L3 and L5 are made of fluorite glass and the lens components L1, L4 and L6 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 14 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 13. As apparent in FIG. 14, the lens system has superior correction for these aberrations.

FIG. 15 shows a fourth version of the second embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.5002 mm in front of the object end surface of the third lens component L3. The third lens group G3 comprises sixth and seventh lens components L6 and L7.

The lens system as shown in FIG. 15 is substantially described in Table VIII.

                  TABLE VIII     ______________________________________     F No. = 2.5 Angle of View = 34.52°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 15.2843     L1                         d.sub.1  = 3.2729                                              1.47454              S2     r.sub.2  = -39.1538                                d.sub.2  = 0.8806              S3     r.sub.3  = -17.6291     L2                         d.sub.3  = 1.0014                                              1.44491              S4     r.sub.4  = 19.6384                                d.sub.4  = 2.4132              S5     r.sub.5  = 15.3904     L3                         d.sub.5  = 4.0135                                              1.44491              S6     r.sub.6  = -10.1601                                d.sub.6  = 0.7501              S7     r.sub.7  = -8.9005     L4                         d.sub.7  = 0.9999                                              1.47454              S8     r.sub.8  = 13.9973                                d.sub.8  = 0.7501              S9     r.sub.9  = 14.4284     L5                         d.sub.9  = 5.2275                                              1.44491              S10    r.sub.10  = -13.4599                                d.sub.10  = 0.0998              S11    r.sub.11  = 16.0753     L6                         d.sub.11  = 7.1184                                              1.47454              S12    r.sub.12  = -81.3659                                d.sub.12  = 2.0295              S13    r.sub.13  = -10.3278     L7                         d.sub.13  = 0.9998                                              1.47454              S14    r.sub.14  = 24.4406                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 -160.938 21.639  -50.490                                   14.523                                         -11.270                                                16.645     ______________________________________

The lens system depicted in FIG. 15 and described in Table VIII has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     -0.16  1.19      -0.51  1.49     1.92  1.30     ______________________________________

As apparent from the above, the lens system shown in FIG. 15 satisfies the conditions (I)-(VI). Together, the lens components L2, L4 and L6 are made of fluorite glass and the lens components L1, L3, L5 and L7 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 16 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 15. As apparent in FIG. 16, the lens system has superior correction for these aberrations.

FIG. 17 shows a fourth version of the second embodiment of the present invention in which a lens stop D is stationarily disposed at distance of 0.5000 mm in front of the object end surface of the third lens component L3. The second lens group G2 includes doublet comprising a fourth and fifth lens components L4 and L5 cemented together. The third lens group G3 comprises a sixth and seventh lens components L6 and L7.

The lens system as shown in FIG. 17 is substantially described in Table IX.

                  TABLE IX     ______________________________________     F No. = 2.502 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 13.6448     L1                         d.sub.1  = 3.2767                                              1.47454              S2     r.sub.2  = -153.8442                                d.sub.2  = 1.1951              S3     r.sub.3  = -20.2033     L2                         d.sub.3  = 3.0628                                              1.44491              S4     r.sub.4  = 11.3635                                d.sub.4  = 2.0021              S5     r.sub.5  = 12.2834     L3                         d.sub.5  = 4.4735                                              1.44491              S6     r.sub.6  = -10.0271                                d.sub.6  = 0.7629              S7     r.sub.7  = -8.9750     L4                         d.sub.7  = 1.0000                                              1.47454              S8     r.sub.8  = 16.8757                                d.sub.8  = 0              S9     r.sub.9  = 16.8757     L5                         d.sub.9  = 4.5733                                              1.44491              S10    r.sub.10  = -14.4174                                d.sub.10  = 0.1000              S11    r.sub.11  = 13.8753     L6                         d.sub.11  = 6.7028                                              1.47454              S12    r.sub.12  = -57.8863                                d.sub.12  = 3.3926              S13    r.sub.13  = -10.7576     L7                         d.sub.13  = 1.0000                                              1.47454              S14    r.sub.14  = 24.4074                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 -46.818  19.074  -198.077                                   13.154                                         -12.227                                                18.340     ______________________________________

The lens system depicted in FIG. 15 and described in Table VIII has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     -0.55  1.35      -0.13  1.45     1.56  1.04     ______________________________________

As apparent from the above, the lens system shown in FIG. 17 satisfies the conditions (I)-(VI). Together, the lens components L2, L4 and L6 are made of fluorite glass and the lens components L1, L3, L5 and L7 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L3 and L4 and between the second and third lens components L4 and L5.

FIG. 18 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 17. As apparent in FIG. 18, the lens system has superior correction for these aberrations.

FIGS. 19-22 show various versions of a third embodiment of the present invention. The lens systems are composed of three lens groups, namely first and second and third lens groups G1, G2 and G3 arranged along the optical axis X in order from the object end to the image end. The first lens group G1 comprises three, namely, in order from the object end, first, second and third, lens components L1, L2 and L3. The second lens group G2 comprises three, namely, in order from the object end, a fourth bi-convex lens component L4, a fifth bi-concave lens component L5 and a sixth bi-convex lens component L6. The third lens group G3 comprises one or two, namely seventh and eighth, lens component L7 and L8. A lens stop D is stationarily disposed between the first and second lens groups G1 and G2. A parallel flat cover plate G4 is disposed at a certain distance behind the image end surface of the seventh or eighth lens component L7 or L8. These optical components including the lens components L1-L8 and the parallel flat cover plate G4 are in fixed relation.

FIG. 19 shows a first version of the third embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.5001 mm in front of the object end surface of the fourth lens component L4. The third lens group G3 comprises a seventh single lens components L7.

The lens system as shown in FIG. 19 is substantially described in Table X.

                  TABLE X     ______________________________________     F No. = 2.504 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 28.1052     L1                         d.sub.1  = 2.0000                                              1.47454              S2     r.sub.2  = 19.1933                                d.sub.2  = 25.0000              S3     r.sub.3  = 20.7703     L2                         d.sub.3  = 4.3030                                              1.44491              S4     r.sub.4  = -15.9983                                d.sub.4  = 0.5844              S5     r.sub.5  = -13.6918     L3                         d.sub.5  = 1.0000                                              1.44491              S6     r.sub.6  = 112.4142                                d.sub.6  = 1.50001              S7     r.sub.7  = 12.6673     L4                         d.sub.7  = 4.9154                                              1.47454              S8     r.sub.8  = -12.7708                                d.sub.8  = 0.5843              S9     r.sub.9  = -11.2291     L5                         d.sub.9  = 1.0000                                              1.44491              S10    r.sub.10  = 9.2240                                d.sub.10  = 0.5001              S11    r.sub.11  = 9.3296     L6                         d.sub.11  = 6.1444                                              1.47454              S12    r.sub.12  = -15.4457                                d.sub.12  = 6.2607              S13    r.sub.13  = -6.8811     L7                         d.sub.13  = 1.2501                                              1.47454              S14    r.sub.14  = -22.0059                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 151.471  20.935  -21.639                                   15.281                                         -10.681                                                14.241     ______________________________________

The lens system depicted in FIG. 19 and described in Table X has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     ______________________________________     0.17   1.23      -1.19  1.37     1.96  1.47     ______________________________________

As apparent from the above, the lens system shown in FIG. 19 satisfies the conditions (I)-(VI). Together, the lens components L2, L4 and L6 are made of fluorite glass and the lens components L1, L3, L5 and L7 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L4 and L5 and between the second and third lens components L5 and L6.

FIG. 20 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 19. As apparent in FIG. 20, the lens system has superior correction for these aberrations.

FIG. 21 shows a second version of the third embodiment of the present invention in which a lens stop D is stationarily disposed at a distance of 0.5000 mm in front of the object end surface of the fourth lens component L4. The third lens group G3 comprises seventh and eighth lens components L7 and L8.

The lens system as shown in FIG. 21 is substantially described in Table XI.

                  TABLE XI     ______________________________________     F No. = 2.059 Angle of View = 41.80°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 18.8353     L.sub.1                    d.sub.1  = 12.43353                                              1.47454              S2     r.sub.2  = 13.0019                                d.sub.2  = 23.83678              S3     r.sub.3  = -8.0093     L.sub.2                    d.sub.3  = 0.99913                                              1.44491              S4     r.sub.4  = 9.8105                                d.sub.4  = 0.63775              S5     r.sub.5  = 19.8380     L.sub.3                    d.sub.5  = 3.30476                                              1.44491              S6     r.sub.6  = -8.6331                                d.sub.6  = 1.00041              S7     r.sub.7  = 9.3566     L.sub.4                    d.sub.7  = 3.93042                                              1.47454              S8     r.sub.8  = -8.1667                                d.sub.8  = 0.49975              S9     r.sub.9  = -7.0495     L.sub.5                    d.sub.9  = 0.99974                                              1.44491              S10    r.sub.10  = 8.3375                                d.sub.10  = 0.50078              S11    r.sub.11  = 8.8786     L.sub.6                    d.sub.11  = 4.05854                                              1.47454              S12    r.sub.12  = -9.1986                                d.sub.12  = 0.09991              S13    r.sub.13  = 18.7655     L.sub.7                    d.sub.13  = 3.28991                                              1.47454              S14    r.sub.14  = -10.4052                                d.sub.14  = 0.75135              S15    r.sub.15  = -7.0579     L.sub.8                    d.sub.15  = 1.56100                                              1.47454              S16    r.sub.16  = 33.8019                                d.sub.16  = 2.0000              S17    r.sub.17  = ∞     G4                         d.sub.17  = 2.5500                                              1.47454              S18    r.sub.18  = ∞     ______________________________________     F     F1      F2      F3      f1    f2    f3     14.38 -55.308 14.673  -110.615                                   10.556                                         -7.931                                               10.869     ______________________________________

The lens system depicted in FIG. 21 and described in Table VIII has the following parameters described as follows:

    ______________________________________     F/F1   F/F2      F/F3   F2/f1    |F2/f2|                                            F2/f3     -0.26  0.98      -0.13  1.39     1.85  1.35     ______________________________________

As apparent from the above, the lens system shown in FIG. 19 satisfies the conditions (I)-(VI). Together, the lens components L3, L4, L6 and L7 are made of fluorite glass and the lens components L1, L2, L5 and L8 and the cover plate G4 are made of silicate glass. The dispersion is different between the first and second lens components L4 and L5 and between the second and third lens components L5 and L6.

FIG. 22 shows diagrams illustrating aberrations, such as spherical aberrations for i-, g-, e- and C-spectra, sagittal and tangential astigmatism, distortion for i-spectrum and magnification color aberrations for g-, e- and C-spectra of the lens system shown in FIG. 21. As apparent in FIG. 22, the lens system has superior correction for these aberrations.

As apparent from the above embodiments, the lens system of the present invention may be designed for a wide range of angles of view by satisfying the above conditions.

FIG. 23 shows transmittance of various glass materials including fluorite glass and silicate glass. The transmittance was measured with various parallel plates of a thickness of 10 mm. As apparent from FIG. 23, each of the fluorite glass and silicate glass has a transmittance greatly higher over a range of ultraviolet rays than glass materials such as BK-7 and BK-2 which are general as optical lens materials. Specifically, the transmittance of each of the fluorite glass and silicate glass is higher than 80% over a range of wavelength from 300 to 400 nm. Though not shown in FIG. 23, each of the fluorite glass and silicate glass has a transmittance higher than 80% over a range of wavelength from 400 to 800 nm. Practically, the lens system may be designed with well corrected aberrations as long as lens components made of materials having transmittance higher than 50% for visible rays and ultraviolet rays are used.

Generally, the smaller the difference in dispersion among materials of lens components is, the harder the lens system is corrected in aberrations.

It is to be understood that although the present invention has been described with regard to preferred embodiments thereof, various other embodiments and variants may occur to those skilled in the art, which are within the scope and spirit of the invention, and such other embodiments and variants are intended to be covered by the following claims. 

What is claimed is:
 1. A fixed focal length wide angle image forming optical lens system comprising in order from the object end a first lens group of at least two components, a second lens group which has a positive focal length and comprises in order from the object end a first component of positive power, a second component of negative power and a third component of positive power, and a third lens group of at least one component, said optical lens system satisfying the following conditions:

    -0.75<F/F1<0.75

    0.3<F/F2<1.55

    -1.50<F/F3<0.15

    0.9<F2/f1<5.0

    1.2<|F2/f2|<7

    0.9<F2/f3<2.4

where F is the overall focal length of the lens system, F1, F2 and F3 are the focal length of the first, second and third lens groups, respectively, and f1, f2 and f3 are the focal length of the first, second and third components of the second lens group, respectively wherein all lens component materials have dispersion differences of no greater than 0.0055.
 2. An image forming optical lens system as defined in claim 1, further comprising a lens stop disposed between said two components of said first lens group.
 3. An image forming optical lens system as defined in claim 2 substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 23.9660     L.sub.1                    d.sub.1  = 9.9262                                              1.47454              S2     r.sub.2  = 11.2800                                d.sub.2  = 25.9857              S3     r.sub.3  = -52.4481     L.sub.2                    d.sub.3  = 3.7473                                              1.44491              S4     r.sub.4  = -22.0621                                d.sub.4  = 0.1              S5     r.sub.5  = 15.9527     L.sub.3                    d.sub.5  = 5.4006                                              1.44491              S6     r.sub.6  = -16.6354                                d.sub.6  = 0.7501              S7     r.sub.7  = -13.0937     L.sub.4                    d.sub.7  = 1.0                                              1.47454              S8     r.sub.8  = 9.5032                                d.sub.8  = 1.0001              S9     r.sub.9  = 11.3864     L.sub.5                    d.sub.9  = 6.7394                                              1.44491              S10    r.sub.10  = -11.1132                                d.sub.10  = 0.9999              S11    r.sub.11  = -13.9526     L.sub.6                    d.sub.11  = 1.0                                              1.47454              S12    r.sub.12  = 9.6928                                d.sub.12  = 1.0              S13    r.sub.13  = 11.2385     L.sub.7                    d.sub.13  = 4.8019                                              1.44491              S14    r.sub.14  = ∞                                d.sub.14  = 2.0              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.55                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1      F2      F3      f1    f2    f3     25.76 57.244  22.4    -24.769 19.31 -11.429                                               13.913     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object and to the image end of the lens system, and N is defined as a refractive index of the lens material.
 4. An image forming optical lens system as defined in claim 2 substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 22.6687     L.sub.1                    d.sub.1  = 10.000                                              1.47454              S2     r.sub.2  = 10.5512                                d.sub.2  = 26.3689              S3     r.sub.3  = 212.6157     L.sub.2                    d.sub.3  = 3.7200                                              1.44491              S4     r.sub.4  = -17.9567                                d.sub.4  = 0.100              S5     r.sub.5  = 17.2749     L.sub.3                    d.sub.5  = 5.0841                                              1.44491              S6     r.sub.6  = -17.7102                                d.sub.6  = 0.7500              S7     r.sub.7  = -14.0756     L.sub.4                    d.sub.7  = 1.0000                                              1.47454              S8     r.sub.8  = 8.164                                d.sub.8  = 0              S9     r.sub.9  = 8.164     L.sub.5                    d.sub.9  = 8.3860                                              1.44491              S10    r.sub.10  = -11.8778                                d.sub.10  = 0.9999              S11    r.sub.11  = -12.4212     L.sub.6                    d.sub.11  = 1.0000                                              1.47454              S12    r.sub.12  = 10.6415                                d.sub.12  = 1.0000              S13    r.sub.13  = 11.8335     L.sub.7                    d.sub.13  = 4.0417                                              1.44491              S14    r.sub.14  = -1764.3175                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1      F2      F3      f1    f2    f3     25.75 52.551  22.391  -23.624 20.542                                         -10.765                                               12.509     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 5. An image forming optical lens system as defined in claim 2, substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 24.9171     L.sub.1                    d.sub.1  = 9.9358                                              1.47454              S2     r.sub.2  = 11.4855                                d.sub.2  = 26.4008              S3     r.sub.3  = 320.9305     L.sub.2                    d.sub.3  = 3.567                                              1.44491              S4     r.sub.4  = -19.9207                                d.sub.4  = 0.1001              S5     r.sub.5  = 13.9293     L.sub.3                    d.sub.5  = 6.6087                                              1.44491              S6     r.sub.6  = -13.2100                                d.sub.6  = 0              S7     r.sub.7  = -13.2100     L.sub.4                    d.sub.7  = 1.0131                                              1.47454              S8     r.sub.8  = 9.6419                                d.sub.8  = 1.0061              S9     r.sub.9  = 9.8346     L.sub.5                    d.sub.9  = 6.3403                                              1.44491              S10    r.sub.10  = -14.4150                                d.sub.10  = 1.0033              S11    r.sub.11  = -11.8551     L.sub.6                    d.sub.11  = 1.0006                                              1.47454              S12    r.sub.12  = 9.5828                                d.sub.12  = 1.0031              S13    r.sub.13  = 11.6447     L.sub.7                    d.sub.13  = 3.8428                                              1.44491              S14    r.sub.14  = -7240.6751                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1      F2      F3      f1    f2    f3     25.76 66.051  20.125  -20.608 16.496                                         -11.5 14.273     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 6. An image forming optical lens system as defined in claim 2, substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 22.4734     L.sub.1                    d.sub.1  = 10.0088                                              1.47454              S2     r.sub.2  = 11.0857                                d.sub.2  = 23.4071              S3     r.sub.3  = 132.1196     L.sub.2                    d.sub.3  = 3.4406                                              1.44491              S4     r.sub.4  = -20.0776                                d.sub.4  = 0.1000              S5     r.sub.5  = 14.6176     L.sub.3                    d.sub.5  = 6.1359                                              1.44491              S6     r.sub.6  = -11.7794                                d.sub.6  = 0              S7     r.sub.7  = -11.7794     L.sub.4                    d.sub.7  = 0.9498                                              1.47454              S8     r.sub.8  = 8.4994                                d.sub.8  = 0              S9     r.sub.9  = 8.4994     L.sub.5                    d.sub.9  = 6.9201                                              1.44491              S10    r.sub.10  = -14.7415                                d.sub.10  = 1.3550              S11    r.sub.11  = -12.2623     L.sub.6                    d.sub.11  = 4.8411                                              1.47454              S12    r.sub.12  = 9.4213                                d.sub.12  = 1.2466              S13    r.sub.13  = 11.3787     L.sub.7                    d.sub.13  = 4.2154                                              1.44491              S14    r.sub.14  = 15532.5120                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 61.310   21.107  -21.458                                   15.917                                         -10.148                                                13.275     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 7. An image forming optical lens system as defined in claim 1, further comprising a lens stop disposed between said first lens group and said second lens group.
 8. An image forming optical lens system as defined in claim 7, substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 23.8147     L.sub.1                    d.sub.1  = 1.0026                                              1.47454              S2     r.sub.2  = 10.0929                                d.sub.2  = 1.2583              S3     r.sub.3  = 12.4516     L.sub.2                    d.sub.3  = 4.2303                                              1.44491              S4     r.sub.4  = 142.6490                                d.sub.4  = 9.3229              S5     r.sub.5  = 17.2963     L.sub.3                    d.sub.5  = 3.6873                                              1.44491              S6     r.sub.6  = -12.1061                                d.sub.6  = 1.2596              S7     r.sub.7  = -9.8721     L.sub.4                    d.sub.7  = 1.1823                                              1.47454              S8     r.sub.8  = 9.6330                                d.sub.8  = 1.2458              S9     r.sub.9  = 19.9700     L.sub.5                    d.sub.9  = 4.2708                                              1.44491              S10    r.sub.10  = -11.6384                                d.sub.10  = 0.1003              S11    r.sub.11  = 18.4670     L.sub.6                    d.sub.11  = 5.0541                                              1.47454              S12    r.sub.12  = -10.3953                                d.sub.12  = 0.7458              S13    r.sub.13  = -11.0881     L.sub.7                    d.sub.13  = 5.3058                                              1.44491              S14    r.sub.14  = 9.8022                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1      F2      F3      f1    f2    f3     25.76 143.056 33.013  -99.038 16.507                                         -9.914                                               17.194     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 9. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.504 Angle of View = 34.48°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 14.2465     L.sub.1                    d.sub.1  = 4.0484                                              1.47454              S2     r.sub.2  = -19.6229                                d.sub.2  = 0.5644              S3     r.sub.3  = -15.6487     L.sub.2                    d.sub.3  = 1.0000                                              1.44491              S4     r.sub.4  = 24.5485                                d.sub.4  = 1.7371              S5     r.sub.5  = 9.8040     L.sub.3                    d.sub.5  = 4.1775                                              1.44491              S6     r.sub.6  = -11.6842                                d.sub.6  = 0.5320              S7     r.sub.7  = -10.2333     L.sub.4                    d.sub.7  = 3.2945                                              1.47454              S8     r.sub.8  = 7.8683                                d.sub.8  = 1.3165              S9     r.sub.9  = 23.6511     L.sub.5                    d.sub.9  = 3.1266                                              1.44491              S10    r.sub.10  = -17.6213                                d.sub.10  = 1.0506              S11    r.sub.11  = 8.8540     L.sub.6                    d.sub.11  = 4.5398                                              1.47454              S12    r.sub.12  = 7.5565                                d.sub.12  = 2.0000              S13    r.sub.13  = ∞     G4                         d.sub.13  = 2.5500                                              1.47454              S14    r.sub.14  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 117.045  35.764  858.333                                   12.505                                         -8.941 23.223     ______________________________________

where the optical lens system comprises lens components L1 to L6 and an optical component G4 having surfaces S1 to S14, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 10. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.5 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 14.7844     L.sub.1                    d.sub.1  = 4.0110                                              1.47454              S2     r.sub.2  = -20.4636                                d.sub.2  = 0.4906              S3     r.sub.3  = -18.2579     L.sub.2                    d.sub.3  = 1.0000                                              1.44491              S4     r.sub.4  = 32.3312                                d.sub.4  = 2.0142              S5     r.sub.5  = 10.4750     L.sub.3                    d.sub.5  = 4.6115                                              1.44491              S6     r.sub.6  = -7.5771                                d.sub.6  = 0              S7     r.sub.7  = -7.5771     L.sub.4                    d.sub.7  = 3.5961                                              1.47454              S8     r.sub.8  = 7.6524                                d.sub.8  = 1.5227              S9     r.sub.9  = 43.7342     L.sub.5                    d.sub.9  = 2.9291                                              1.44491              S10    r.sub.10  = -17.1000                                d.sub.10  = 0.1000              S11    r.sub.11  = 8.7618     L.sub.6                    d.sub.11  = 5.0002                                              1.47454              S12    r.sub.12  = 7.4823                                d.sub.12  = 2.0000              S13    r.sub.13  = ∞     G4                         d.sub.13  = 2.5500                                              1.47454              S14    r.sub.14  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 71.528   50.490  429.167                                   10.607                                         -7.570 27.742     ______________________________________

where the optical lens system comprises lens components L1 to L6 and an optical component G4 having surfaces S1 to S14, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 11. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.505 Angle of View = 34.52°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 15.2843     L.sub.1                    d.sub.1  = 3.2729                                              1.47454              S2     r.sub.2  = -39.1538                                d.sub.2  = 0.8806              S3     r.sub.3  = -17.6291     L.sub.2                    d.sub.3  = 1.0014                                              1.44491              S4     r.sub.4  = 19.6384                                d.sub.4  = 2.4132              S5     r.sub.5  = 15.3904     L.sub.3                    d.sub.5  = 4.0135                                              1.44491              S6     r.sub.6  = -10.1601                                d.sub.6  = 0.7501              S7     r.sub.7  = -8.9005     L.sub.4                    d.sub.7  = 0.9999                                              1.47454              S8     r.sub.8  = 13.9973                                d.sub.8  = 0.7501              S9     r.sub.9  = 14.4284     L.sub.5                    d.sub.9  = 5.2275                                              1.44491              S10    r.sub.10  = -13.4599                                d.sub.10  = 0.0998              S11    r.sub.11  = 16.0753     L.sub.6                    d.sub.11  = 7.1184                                              1.47454              S12    r.sub.12  = -81.3659                                d.sub.12  = 2.0295              S13    r.sub.13  = -10.3278     L.sub.7                    d.sub.13  = 0.9998                                              1.47454              S14    r.sub.14  = 24.4406                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.76 -160.938 21.639  -50.490                                   14.523                                         -11.270                                                16.645     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component by G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 12. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.502 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 13.6448     L.sub.1                    d.sub.1  = 3.2767                                              1.47454              S2     r.sub.2  = -153.8442                                d.sub.2  = 1.1951              S3     r.sub.3  = -20.2033     L.sub.2                    d.sub.3  = 3.0628                                              1.44491              S4     r.sub.4  = 11.3635                                d.sub.4  = 2.0021              S5     r.sub.5  = 12.2834     L.sub.3                    d.sub.5  = 4.4735                                              1.44491              S6     r.sub.6  = -10.0271                                d.sub.6  = 0.7629              S7     r.sub.7  = -8.9750     L.sub.4                    d.sub.7  = 1.0000                                              1.47454              S8     r.sub.8  = 16.8757                                d.sub.8  = 0              S9     r.sub.9  = 16.8757     L.sub.5                    d.sub.9  = 4.5733                                              1.44491              S10    r.sub.10  = -14.4174                                d.sub.10  = 0.1000              S11    r.sub.11  = 13.8753     L.sub.6                    d.sub.11  = 6.7028                                              1.47454              S12    r.sub.12  = -57.8863                                d.sub.12  = 3.3926              S13    r.sub.13  = -10.7576     L.sub.7                    d.sub.13  = 1.0000                                              1.47454              S14    r.sub.14  = 28.4074                                d.sub.14  = 2.000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 -46.818  19.074  -198.077                                   13.154                                         -12.227                                                18.340     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 13. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.504 Angle of View = 34.50°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 28.0152     L.sub.1                    d.sub.1  = 2.0000                                              1.47454              S2     r.sub.2  = 19.1933                                d.sub.2  = 25.0000              S3     r.sub.3  = 20.7703     L.sub.2                    d.sub.3  = 4.3030                                              1.44491              S4     r.sub.4  = -15.9983                                d.sub.4  = 0.5844              S5     r.sub.5  = -13.6918     L.sub.3                    d.sub.5  = 1.0000                                              1.44491              S6     r.sub.6  = 112.4142                                d.sub.6  = 1.50001              S7     r.sub.7  = -12.6673     L.sub.4                    d.sub.7  = 4.9154                                              1.47454              S8     r.sub.8  = -12.7708                                d.sub.8  = 0.5843              S9     r.sub.9  = -11.2291     L.sub.5                    d.sub.9  = 1.0000                                              1.44491              S10    r.sub.10  = 9.2240                                d.sub.10  = 0.5001              S11    r.sub.11  = 9.3296     L.sub.6                    d.sub.11  = 6.1444                                              1.47454              S12    r.sub.12  = -15.4457                                d.sub.12  = 6.2607              S13    r.sub.13  = -6.8811     L.sub.7                    d.sub.13  = 1.2501                                              1.47454              S14    r.sub.14  = 22.0059                                d.sub.14  = 2.0000              S15    r.sub.15  = ∞     G4                         d.sub.15  = 2.5500                                              1.47454              S16    r.sub.16  = ∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     25.75 151.471  20.935  -21.639                                   15.281                                         -10.681                                                14.241     ______________________________________

where the optical lens system comprises lens components L1 to L7 and an optical component G4 having surfaces S1 to S16, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 14. An image forming optical lens system as defined in claim 7 substantially as described:

    ______________________________________     F No. = 2.059 Angle of View = 41.80°     ______________________________________             Radius of    Axial Distance     Component             Curvature (mm)                          Between Surfaces (mm)                                          N     ______________________________________              S1     r.sub.1  = 18.8353     L.sub.1                    d.sub.1  = 12.43353                                              1.47454              S2     r.sub.2  = 13.0019                                d.sub.2  = 23.83678              S3     r.sub.3  = -8.0093     L.sub.2                    d.sub.3  = 0.99913                                              1.44491              S4     r.sub.4  = 9.8105                                d.sub.4  = 0.63775              S5     r.sub.5  = 19.8380     L.sub.3                    d.sub.5  = 3.30476                                              1.44491              S6     r.sub.6  = -8.6331                                d.sub.6  = 1.00041              S7     r.sub.7  = 9.3566     L.sub.4                    d.sub.7  = 3.93042                                              1.47454              S8     r.sub.8  = -8.1667                                d.sub.8  = 0.49975              S9     r.sub.9  = -7.0495     L.sub.5                    d.sub.9  = 0.99974                                              1.44491              S10    r.sub.10  = 8.3375                                d.sub.10  = 0.50078              S11    r.sub.11  = 8.8786     L.sub.6                    d.sub.11  = 4.05854                                              1.47454              S12    r.sub.12  = -9.1986                                d.sub.12  = 0.09991              S13    r.sub.13  = 18.7655     L.sub.7                    d.sub.13  = 3.28991                                              1.47454              S14    r.sub.14  = -10.4052                                d.sub.14  = 0.75135              S15    r.sub.15  = -7.0579     L.sub.8                    d.sub.15  = 1.56100                                              1.47454              S16    r.sub.16  = 33.8019                                d.sub.16  = 2.0000              S17    r.sub.17  = ∞     G4                         d.sub.17  = 2.5500                                              1.47454              S18    r.sub.18  =∞     ______________________________________     F     F1       F2      F3     f1    f2     f3     14.38 -55.308  14.673  -110.615                                   10.556                                         -7.931 10.869     ______________________________________

where the optical lens system comprises lens components L1 to L8 and an optical component G4 having surfaces S1 to S18, and the radius of each surface is given by r followed by an arabic numeral progressively from the object end to the image end of the lens system, and N is defined as a refractive index of the lens material.
 15. A fixed focal length wide angle image forming optical lens system comprising in order from the object end, a first lens group comprising a first component and a second component; a lens stop disposed between said first component and said second component; a second lens group which has a positive focal length and comprises in order from the object end a first component of positive power, a second component of negative power and a third component of positive power, and a third lens group of at least one component, said optical lens system satisfying the following conditions:

    -0.75<F/F1<0.75

    0.3<F/F2<1.55

    -1.50<F/F3<0.15

    0.9<F2/f1<5.0

    1.2<|F2/f2|<7

    0.9<F2/f3<2.4

where F is the overall focal length of the lens system, F1, F2 and F3 are the focal length of the first, second and third lens groups, respectively, and f1, f2 and f3 are the focal length of the first, second and third components of the second lens group, respectively.
 16. A fixed focal length wide angle image forming optical lens system comprising in order from the object end a first lens group consisting of two components, a second lens group which has a positive focal length and comprises in order from the object end a first component of positive power, a second component of negative power and a third component of positive power, and a third lens group of at least one component, said optical lens system satisfying the following conditions:

    -0.75<F/F1<0.75

    0.3<F/F2<1.55

    -1.50<F/F3<0.15

    0.9<F2/f1<5.0

    1.2<|F2/f2|<7

    0.9<F2/f3<2.4

where F is the overall focal length of the lens system, F1, F2 and F3 are the focal length of the first, second and third lens groups, respectively, and f1, f2 and f3 are the focal length of the first, second and third components of the second lens group, respectively. 